The purpose of this paper is to give an overview of the use and potential of diamond wire for the silicon-shaping process in the PV industry. The current market and future prospects for helping to meet the goals of 2020’s roadmap of thinner wafers and reduced $/W are described.
Predicting what will happen to the global PV market is very nearly an impossible task. Its underlying principles are very similar to the dozens of other electronics markets that IMS Research studies, but the key difference in the PV industry is the very close link to, and ultimate dependence on, government policy. In a few years’ time, the introduction, halting or change (or rumoured change) of a single government’s PV policy will have little effect on the global industry, and the huge swings in demand will be less common and less severe. The reasons for this are clear. First, because of geographic diversification in the industry, a single country will account for a smaller portion of the global total (unlike in 2011, when Germany and Italy accounted for more than half of global demand) and thus individual governments’ policy changes will have a smaller impact. Second, if system prices continue to drop rapidly (and IMS Research believes they will), a growing number of regions will achieve the ‘holy grail’ of grid parity and will thus no longer depend solely on government policy to drive their markets.
The solar photovoltaics market in the United Kingdom was virtually non-existent until April 2010, when the long-awaited feed-in tariff scheme was implemented. Yet, despite coming late to the game, the UK’s solar industry took off immediately, installing more than 80MW in the first 12 months alone. Now, just two years down the line, the market is placed as the world’s eighth largest. This paper will take a look back at how the UK got to this point as well as considering just how bright the future of this fast-paced market will realistically be.
In the photovoltaics industry, contacts to crystalline silicon are typically formed by the firing of screen-printed metal pastes. However, the stability of dielectric surface passivation layers during the high-temperature contact formation has turned out to be a major challenge for some of the best passivating layers, such as intrinsic amorphous silicon. Capping of well-passivating dielectric layers by hydrogen-rich silicon nitride (SiNx), however, has been demonstrated to improve the thermal stability, an effect which can be attributed to the atomic hydrogen (H) diffusing out of the interface during firing, and passivating dangling bonds. This paper presents the results of investigations into the influence of two different dielectric passivation stacks on the firing stability, namely SiNy/SiNx (y < x) and Al2O3/SiNx stacks. Excellent firing stability was demonstrated for both stack systems. Effective surface recombination velocities of < 10cm/s were measured after a conventional co firing process on 1.5Ωcm p-type float-zone silicon wafers for both passivation schemes. On the solar cell level, however, better results were obtained using the Al2O3/SiNx stack, where an efficiency of 19.5% was achieved for a large-area screen-printed solar cell fabricated on conventional Czochralski-grown silicon.
Several PV module producers have performed a carbon footprint analysis and published a sustainability report as part of their corporate social responsibility policy. Comparison of carbon footprint results is difficult because several international standards and life cycle assessment (LCA) databases are used. No product footprint category rules (PFCR) or product category rules (PCRs) for photovoltaics exist, so LCAs are performed with varying underlying assumptions. Furthermore, a fair comparison can only be made when all environmental footprints of a product are taken into account.
The PV industry is undergoing dramatic changes. Like a carnival ride gone dreadfully wrong, exhilaration has been supplanted by dread; joy has been replaced by fear. Just look around you – provided you are able to turn your head to defy the g-forces acting upon you as we bank and turn wildly along. You will see PV companies closing their doors for good. You will see extraordinarily talented people throughout the supply chain, shifting positions everywhere and looking for safe-haven jobs. And you will also see once-leading PV companies burning cash and losing their status as ‘bankable’. Everywhere we turn, we see companies in the supply chain shuttering production as if to balance markets.
In trying to introduce its relatively new technology to traditional utility customers, the photovoltaic industry often finds itself in the awkward position of trying to sell a product to a customer who may not want to buy. The up-front capital costs of new solar plants (that deliver power only intermittently) can be less than appealing. Large-scale grid integration will therefore be accelerated by PV technologies that best fit the profile of traditional power sources. In addition to low cost, this includes high capacity factors and the ability to better match demand during daylight hours.
Concentrator photovoltaic (CPV) power plants are now being integrated into the grid at megawatt scales. By performing light collection using acrylic, silicone, or glass optics instead of semiconductors, the material cost balance of PV is fundamentally shifted. The world’s most efficient solar cells can then be employed, and maintaining tracking of the sun becomes economically favorable across vast sunny locales worldwide. With AC system efficiencies in excess of 25%, the resulting CPV power plants produce high energy yields throughout the year and deliver the high capacity factors demanded by utility customers. Since semiconductors are a minority component cost, manufacturing capital costs are lower than for any other PV technology, allowing for rapid scale-up and field deployment. This article will describe the state of the art of CPV technology, field performance results, and the outlook for near-term deployments.
This paper presents a novel glue-membrane integrated backsheet specifically for PV modules, which has been designed and fabricated by utilizing a flow-tangent cast roll-to-roll coating process combined with a plasma technique. Polyethylene terephthalate (PET) is adopted as a substrate and is surface activated and etched by atmospheric plasma. Then a special coating formulation containing reactive fluoropolymers is applied to both sides of the PET, followed by thermal curing, resulting in a glue-membrane integrated coating layer with a polyurethane structure. Finally, a monolayer of silane molecules is grafted onto the surface via plasma-enhanced deposition to provide the surface medium with surface energy, rendering excellent long-term adhesion to ethylene vinyl acetate (EVA).
The improved performance and reduced manufacturing costs of photovoltaic (PV) modules that have been achieved in recent years have positioned this technology as an economically attractive renewable electric energy source. In order to verify that this also has a positive impact on energy payback time (EPBT) and carbon footprint, the Energy Research Centre of the Netherlands (ECN) has conducted a life cycle analysis (LCA) for REC Peak Energy-series PV modules produced by Renewable Energy Corporation (REC). The LCA study was based on a full set of actual production data obtained for the first quarter of 2011from REC’s manufacturing sites. Because REC is an integrated manufacturer, the LCA study includes internal data for the production steps from polysilicon production to module assembly, as well as for all materials and transportation associated with production. ECN used generic figures for installation, operations and recycling together with the REC data to assess the environmental impact indicators. For polysilicon produced in the USA, and for wafers, cells and modules produced in Singapore, an EPBT of 1.2 years was achieved, with a corresponding carbon footprint of 21g CO2-eq/kWh for PV systems located in southern Europe (1700kWh/m2year irradiation). For modules with wafers and cells produced in Norway, the corresponding values were 1.1 years and 18g CO2-eq/kWh. A key contributor in achieving these values is REC’s highly efficient fluidized bed reactor (FBR) process for the production of polysilicon.
For a vertically integrated solar cell production starting with purification of silicon feedstock and ending with the production of solar cells, it is necessary to have control over all possible parameters that may affect yield, efficiency and product quality. This paper presents an approach for tracking products with minimal effort using a contactless technique. The method allows wafers to be virtually reconstructed into bricks and ingots, as well as recognizing the precursor wafer for each solar cell.